This invention relates to hydraulic positive displacement devices, and more specifically to planetary hydraulic motors.
There is known an internal-gear type hydraulic pump or more (U.S. Pat. No. 3,087,436; published Apr. 30, 1963, Cl. 418-61) comprising an outer stator gear and an inner star gear disposed eccentrically relative thereto, the spaces between the two gears defining volume chambers of varying volume to convert the pressure energy of the incoming fluid into mechanical energy of the rotating shaft. The volume chambers of this motor are confined at the two sides thereof by a cover plate and a wear plate attached to the housing, the latter accommodating a valving mechanism and a tooth-type coupling intended to translate the compound motion of the inner star gear into shaft rotation.
In this known device a control valve of the valving mechanism is driven by universal-joint connections of the toothed coupling, the teeth thereof being subjected to considerable loads which result in their wear and consequently in a phase displacement of the passage of the working fluid into the volume chambers entailing reduced hydromechanical efficiency of the motor. Another disadvantage is that the valving mechanism featuring the universal-joint connections tends to increase longitudinal dimensions of this hydraulic motor. Therefore, a planetary hydraulic motor of the above construction has low efficiency and reliability and requires that components thereof be manufactured to close tolerances.
Also known is a planetary hydraulic motor (cf. USSR Inventor's Certificate No. 181,977; IPC F 05 B; published in the Bulletin "Discoveries, Inventions, Industrial Designs and Trademarks", No. 10, 1966--in Russian) comprising disposed in one plane two pairs of gears--the outer working one, and the inner driving one, and two cover plates arranged at the outer stator gear with a ring rotor having inner teeth cooperating with the shaft teeth and outer teeth engaging with the teeth of the stator gear to define volume chambers.
In this planetary hydraulic motor the function of distributor is performed by the ring rotor having at the end faces thereof axial passages communicating with the spaces between the teeth. The end face of one of the cover plate contacting the ring rotor is likewise provided with axial passages, some of them being adapted to communicate with a working fluid inlet passageway, the others communicating with a working fluid outlet passageway. A disadvantage inherent in the abovedescribed planetary hydraulic motor resides in a rather low delivery rate thereof caused by the small passage area of the passages provided in the ring rotor and one of the cover plates.
There is further known a planetary hydraulic motor (cf. USSR Inventor's Certificate No. 176,186; IPC F 05 B; published in the Bulletin "Discoveries, Inventions, Industrial Designs and Trademarks" No. 21 of Oct. 26, 1965--in Russian) comprising a ring rotor positioned essentrically relative to a shaft, and an outer stator gear enclosed by two cover plates. A valving mechanism of this motor is fashioned as a stationary disk provided with a series of axial passages and a cylindrical sleeve having at the outer surface thereof helical grooves communicated by radial passages in the ring rotor with volume chambers of the ring rotor and alternately communicating with axial passages of the cover plate, the passages being arranged at 180.degree. relative to the corresponding volume chambers.
The helical sleeve is provided with inner teeth adapted to come into meshing engagement with the teeth of the stationary shaft. The ring rotor of the hydraulic motor is subjected to axially acting forces produced by the pressure of the working fluid in the valving mechanism.
Yet another planetary hydraulic motor (cf. French Pat. No. 2,056,110; published May 14, 1971; IPC F 04 C 1/00) comprises positioned in one plane two gear sets: an inner working one and an outer driving one: two cover plates secured on the outer stator gear with an eccentrically arranged ring rotor interposed between the cover plates, the ring rotor having outer teeth mating with the teeth of the stator gear and inner teeth mating with the teeth of the shaft gear to define volume chamber.
The ring rotor of this planetary hydraulic motor functions as a distributor, an end face of this ring rotor being provided with zigzag grooves in communication with the interteeth space of the volume chambers. A disk member is secured on the shaft to adjoin the grooves, the disk having axial through passages communicated with the zigzag grooves. Arranged between the disk member and the cover plate adjacent thereto are annular passages to feed and discharge the working fluid, the annular passages being separated by an annular wall dividing the volume chambers and effecting the distribution of the working fluid into the volume chambers during the movement of the ring rotor jointly with the disk. This valving mechanism featuring the zigzag grooves on the ring rotor closed by the disk moving jointly with the ring rotor requires close manufacturing tolerances and has an excessive sealing periphery which reduces the delivery rate of the planetary hydraulic rotor. The provision of the zigzag grooves increases the overall dimensions of the motor, while the disk member is subjected to considerable forces exerted thereon by the pressure of the working fluid.
A planetary hydraulic motor which bears closest resemblance to the one to be described in the present description (cf. USSR Inventor's Certificate No. 696,179; IPC F 04 C 1/00; published in the Bulletin "Discoveries, Inventions, Industrial Designs and Trademarks" No. 41 of Nov. 5, 1979--in Russian) comprises a housing having a stator gear, the stator gear being confined on one side by a mounting cover plate and on the other side by a cover plate for feeding a working fluid, a shaft installed in the housing and having a gear secured thereon, a ring rotor arranged eccentrically relative to the shaft and adapted to cooperate with the shaft gear and with the stator gear of the housing. The stator gear and outer teeth of the ring rotor come into a meshing engagement with each other, while the shaft gear and inner teeth of the ring rotor cooperate to define volume chambers receiving an expelling the working fluid supplied by a valving mechanism. The valving mechanism includes secured on the shaft a distributor and arranged in the cover plate for feeding the working fluid a control valve, the distributor and the control valve being adapted to come into contact by their working surfaces having valving ports thereon. The volume chambers are confined on one side by a wear plate fixedly secured on the shaft and on the other side by the distributor. Part of the valving ports (every other valving port) is put in registration with an inlet passageway of the pump, while the other part is arranged in a similar manner against an outlet passageway.
In this planetary hydraulic motor the working surfaces of the distributor and control valve are not relieved of the pressure of the working fluid acting thereon from the side of a nonengageable end face of the control valve, this pressure being created by the leakage of the fluid from the volume chambers. These working surfaces are generally subjected to very high specific loads which result in a premature wear of the above described planetary hydraulic motor.
Another disadvantage of the above planetary hydraulic motor resides in that the valving ports are arranged on the surface of the distributor equidistantly or at a regular angular pitch, which fails to ensure proper timing of supplying the working fluid at the moment when the volume chamber starts to expand or contract resulting in closing the liquid in the volume chambers thereby affecting the efficiency of the planetary hydraulic motor.
This planetary hydraulic motor is not provided with means for adjusting phase displacement of the working fluid entering the volume chambers.
The above planetary hydraulic motor suffers from one more disadvantage residing in that it is not provided with means relieving the axial loads exerted by the pressure of the working fluid on the bearing of the mounting cover plate which requires the employment of an additional thrust bearing. This makes the motor structurally more complicated and adds to the overall weight thereof.